Modern compression-ignition internal combustion engines (hereinafter ‘diesel’ engines) include one or more fuel injectors which are arranged to deliver a shot of fuel at very high pressure into an associated combustion cylinder of the engine. Typically, fuel is distributed to the fuel injectors of the engine from a source of high pressure fuel (for example a high pressure fuel accumulator volume, or ‘common rail’) through a network of high pressure pipes.
FIGS. 1 and 1A show a known arrangement and an enlarged portion thereof respectively in which an injector 2 is supplied with high pressure fuel by a high pressure pipe 4 which defines a fluid passage 5. The injector 2 takes the general form of an elongate injector body 6 which defines a fuel injection nozzle 8 at one end, the lower end as shown in FIG. 1, and a fuel inlet 10 at the end remote from the fuel injection nozzle 8.
The fuel inlet 10 is a projection 12, or stub, that extends at right angles from the longitudinal axis ‘A’ of the fuel injector body 6. The projection 12 defines a fuel inlet passage 14 that opens up to define a socket 16 having a frustoconical sealing surface.
The socket 16 provides a sealing surface for engaging with a rounded end 18 of the high pressure pipe 4. The rounded end 18, or ‘olive’, of the high pressure pipe 4 defines an annular contact ring 22 at which the high pressure pipe 4 engages the socket 16 thus establishing a high pressure seal.
The pipe 4 is biased into engagement with the socket 16 by way of a pipe nut 24. The nut 24 defines a central aperture 26 through which the pipe 4 is received so that the nut 24 is slidable over the pipe 4. The nut 24 carries an internal thread 30 that is engageable with a cooperable thread 32 provided on the outwardly facing surface of the projection 12.
The nut 24 is retained on the pipe 4 by way of the rounded pipe end 18, which has a diameter larger than the diameter of the nut aperture 26. The nut 24 is screw threadedly engageable with the projection 12 by which means the rounded pipe end 18 is forced into engagement with the socket 16 to establish a seal.
A problem exists in the above arrangement in that the effectiveness of the seal may be compromised. For example, the contact ring 22 between the pipe end 18 and the socket 16 may be damaged during handling of the injector 2 and/or the high pressure pipe 4 during engine manufacture or assembly. Similarly, damage to the contact ring 22 may also occur during a maintenance event.
In such circumstances, it is possible for fuel to leak past the contact ring 22 into a chamber 23 defined between the end of the projection 12 and the inside of the nut 24 and also past the threaded engagement of the projection 12 and nut 24, as is shown by the arrows labelled ‘13’. If the injector is installed in such a manner that the inlet end 10 of the injector 2 is housed within a cam cover of an engine, then there exists the potential of engine oil becoming contaminated by fuel leading to severe engine damage.
Alternatively, if the fuel injector inlet end 10 is located outside the confines of the cam cover, fuel may drip onto the engine which presents a waste of fuel and generates odour.